This invention relates generally to the field of medical apparati and more particularly to an apparatus to provide feedback regarding the movement of the body, for example, the lungs and the internal organs while breathing during imaging procedures, such as computer tomographic fluoroscopy.
Computer-aided tomography (CT) fluoroscopy is a technique used in medical diagnostics wherein x-rays impinge onto and are rotated around a patient to give a detailed real-time three-dimensional image of the interior of the body. CT fluoroscopy is especially useful during medical procedures because its rapid data acquisition and interpretation allow a physician to obtain a tissue sample or administer treatment while viewing the image.
CT fluoroscopy operates in two modes: continuous real-time mode and intermittent “quick-check” mode; and of the two continuous CT fluoroscopy results in a greater radiation exposure to both the patient and others in the vicinity of the patient. Quick accurate needle advancement or placement of treatment or biopsy apparatus into the body, moreover, is difficult with continuous CT fluoroscopy, even with a needle-holder or other device that may prevent or at least minimize exposure to the primary beam. Intermittent CT fluoroscopy, on the other hand, substantially decreases both patient and operator exposure to radiation, as a result, this technique is frequently used for incremental needle advancement and rapid verification of needle position during biopsies and/or administration of treatment.
The lungs, the diaphragm, and the upper abdomen move during breathing; thus the displacement of the body and its organs during the breath cycle can be a significant problem during certain medical procedures because target structures, such as lesions and tumors also move during breathing. Intermittent mode CT fluoroscopy allows imaging only in the axial plane with a slice thickness of three to seven millimeters. Inconsistent breath holding by a patient, especially during procedures performed in the area of the thoracic cavity, can cause target structures such as lesions or tumors to move completely out of sight during imaging and intervention. As an example, during normal breathing, tumors in the lung can move from one to three centimeters, and a diaphragm motion can cause the upper abdominal organs to move from one and a half to six centimeters in the superior-inferior direction. Despite instructions to reproducibly and consistently hold her/his breath, there is also a large variation in lung inflation and upper abdominal organ position even in patients with no known lung pathology. Once reproducibility is decreased, the procedures are prolonged and both the patient and medical personnel are exposed to more radiation. There is also the potential for decreased diagnostic yield of the biopsy specimen and higher complication rates.
Thus, accurate and safe CT fluoroscopy-guided percutaneous biopsies of the lung or upper abdomen require a patient to precisely and reproducibly hold or suspend her/his breath. Even healthy patients are unable to reproduce consistent levels of suspended inspiration or expiration without the help of breath-hold monitoring and feedback systems. These breath-hold monitoring systems coordinate the display or view of the area of interest with a feedback system that allows a patient to hold her/his breath at a particular position. Breath-holding monitoring and database systems have been used successfully in radiation therapy for delivery of radiation to selected moving targets thereby decreasing image artifacts secondary to respiratory motion. With breath-hold systems, the position of the diaphragm and internal organs varied less during suspended respirations than without the breath-holding feedback; e.g., average diaphragm motion decreased from 8.3 millimeters to 1.3 millimeters during magnetic resonance, and average diaphragm variability was reduced from 1.4 centimeters to 0.3 centimeters during radiation treatment. The drawback to the systems, however, is that they monitor external changes in body wall girth or position, rather than the actual physical display of the interior portions of the body; although these external changes may be correlated to diaphragm position and internal lesion location, as disclosed in Frolich et al., “A Simple Device For Breath-Level Monitoring During CT” 156 Radiology 235 (1985). Some of these systems, however, use a liquid mercury column respiration monitor, see Jones et al., “A Respiration Monitor For Use With CT Body Scanning And Other Imaging Techniques” 55 British Journal of Radiology 530 (1982). Most of these systems, moreover, linearly correlate the movement of the body to changes in pressure in the transducer, a presumption that is not always accurate. Still other breath holding and monitoring systems are disclosed in U.S. Pat. Nos. 5,363,844 and 5,242,455 and published U.S. patent application Ser. No. 2003/0188757 entitled “CT Integrated Respiratory Monitor”.
There is thus a need for a sensitive, reliable and convenient monitoring system to detect motion and correlate that motion to real-time imaging procedures, such as correlation of the respiratory cycle in CT fluoroscopy-guided procedures, and provide feedback to a patient or other person. The system, moreover, preferably provides for patient and radiologist interaction and is adaptable for use in intermittent mode CT fluoroscopy-guided biopsies of the lung and upper abdomen.